Long Term Tornado Trends

One of several tornadoes observed by the VORTEX-99 team on May 3, 1999, in central Oklahoma. Note the tube-like condensation funnel, attached to the rotating cloud base, surrounded by a translucent dust cloud. From this website. (Photo credit: Wikipedia)

American Meteorological Society President, Dr Marshall Shepherd, seems to think it is unfair to mention low tornado numbers, saying it is an “abuse”.

So I thought it worthwhile to take another look at the stats at the end of 2012.

Figure 1

Figure 2

Figure 1 shows all tornadoes above EF1. (See here, why EF1’s are excluded.) The 10-Year Trend is significantly below the level consistently seen up to 1991, although the high totals in 2011 have inevitably caused a small upwards blip.

We see a similar pattern with the stronger EF3+ tornadoes.

I do not claim to know what will happen to tornado numbers in coming years. And anyone who does is lying.

Does “global warming” cause tornadoes? No. Thunderstorms do. The harder question may be, “Will climate change influence tornado occurrence?” The best answer is: We don’t know. According to the National Science and Technology Council’s Scientific Assessment on Climate Change, “Trends in other extreme weather events that occur at small spatial scales–such as tornadoes, hail, lightning, and dust storms–cannot be determined at the present time due to insufficient evidence.” This is because tornadoes are short-fused weather, on the time scale of seconds and minutes, and a space scale of fractions of a mile across. In contrast, climate trends take many years, decades, or millennia, spanning vast areas of the globe. The numerous unknowns dwell in the vast gap between those time and space scales. Climate models cannot resolve tornadoes or individual thunderstorms. They can indicate broad-scale shifts in three of the four favorable ingredients for severe thunderstorms (moisture, instability and wind shear), but as any severe weather forecaster can attest, having some favorable factors in place doesn’t guarantee tornadoes. Our physical understanding indicates mixed signals–some ingredients may increase (instability), while others may decrease (shear), in a warmer world. The other key ingredient (storm-scale lift), and to varying extents moisture, instability and shear, depend mostly on day-to-day patterns, and often, even minute-to-minute local weather. Finally, tornado recordkeeping itself also has been prone to many errors and uncertainties, doesn’t exist for most of the world, and even in the U. S., only covers several decades in detailed form.

It is worth reemphasizing just how short the record period is. Given that ocean cycles are around 60 years long, it is difficult to see how we can properly monitor trends with less than at least a century worth of data.

All we can reasonably say is that the long term trend, as measured over a 10-Year average, is lower than it has been for much of the period since 1970.

Excellent post, Paul. Mind you, this will disappoint the Green crowd who are really desperate for bad news right now (you’d think people would wonder about that, them always wanting bad news).

Of course when, as and how, the tornado count turns around again, they’ll be back at it, blaming humans. It’s hard to keep solid hatred down (you’d think people would wonder about that, too, the solid hatred these people have for human kind).

A paper published today in Geophysical Research Letters finds tornado activity in the central US is related to phases of the natural Madden-Julian Oscillation (MJO). Prior research has suggested the Madden-Julian Oscillation is modulated by the 11-year solar cycle. ENSO and the Pacific Decadal Oscillation have also been linked to both tornado activity and solar activity. This begs the question, are changes in solar activity a factor in explaining changes in tornado activity?

In 2011 all we ever heard from the climate fear propaganda media was that the increased number of tornadoes that year was “consistent with what scientists tell us to expect because of global warming” . The number of times the media propaganda pushed this theme was absurd. Now after the very low number of tornadoes in 2012 and starting out 2013 the media is virtually silent about any connection between global warming and tornadoes. The main stream media has no credibity whatsoever in reporting on climate issues. They simply are engaged in a blatant propaganda campaign in support of government imposition of ridiculous requirements upon society based on clearly flawed climate fear claims which are unconnected to any kind of “science”.

Key point : tornadoes have declined. NOAA conveniently see “little” change. Use of such vague adjectives is not scientific. What they are trying to do is minimise the decline. I’m sure if it was in the other direction it would be significant.

However Paul , please get up to speed on data processing. Once again you are not centring your running means which gives the false impression your average results run up to date. They do not , they stop five years, and this may be significant.

Second error you insist on using running means as a filter and they are an awful filter. Here is an example from a recent post here by Wermer. I added a proper filter and it can be seen that beautifully the running mean actually gets most of the short term variation totally inverted !!

The only reason you runny mean looks a little bit like it follows the data is because it both inverts and shifts it (due to your not centring).

If you really can’t do anything more complicated than a running mean, at least do a triple running mean as I did in the plot here. Divide window length at each step by 1.3371 (as near as you can) and do three successive running means. This gives quite a good filter that does not invert stuff.

I expect that if the ‘plateau’ turns into a more obvious decline we will see tornado count rising again. There is a hint of this since 2005. That is why it is important to align the end of your filter correctly. The last runny mean value you have is for 2007 NOT 2012.

Cooling periods seem to present more tornadoes, warming periods less. The slight up turn may be another indication that we are entering a new cooling period.

Looks to me like US hurricane activity may well be higher in periods of global cooling, and vice versa. I recall a Klotzbach and Gray paper some years ago that pointed out how US landfall hurricanes were associated with cooling not warming. The ACE index which has declined so much recently might be worth looking at to see if global storms too are following the same pattern.

Looks to me like US hurricane activity may well be higher in periods of global cooling, and vice versa. I recall a Klotzbach and Gray paper some years ago that pointed out how US landfall hurricanes were associated with cooling not warming. The ACE index which has declined so much recently might be worth looking at to see if global storms too are following the same pattern.

=========

Mike, not sure where you see that. I’d be inclined to say hurricanes are very tightly tied to surface temperature, probably tornadoes being the opposite or more like tied to rate of change of temp than temperature itself.

These people think they’re playing a game, where they win or the planet loses… or something. What they don’t seem to understand is that we, skeptics, are not (usually) playing a game. We’re pointing out inconsistencies or errors in conclusions that pretty much nullify all the alarm. I suppose a few people on the skeptic side are playing a game, but sometimes it’s just too easy.

So calling it an “abuse” is essentially saying “You’re cheating at our game!” — which only makes sense if you’re actually playing.

By the way, it’s an “abuse” to continually find Hockey Sticks in all temperature reconstruction, too… but instead of just whining about it the skeptic side has debunked them with, you know, data and stuff.

Which means, according to the precautionary principle, a worst case scenario should be assumed, that is, tornado occurrence may skyrocket if we do not pay penance. Of course, it may do that even if we do, therefore we are doomed anyway. Press release fixed, mission accomplished.

“…three of the four favorable ingredients for severe thunderstorms (moisture, instability and wind shear), but as any severe weather forecaster can attest, having some favorable factors in place doesn’t guarantee tornadoes. Our physical understanding indicates mixed signals–some ingredients may increase (instability), while others may decrease (shear), in a warmer world. The other key ingredient (storm-scale lift)…

If I can throw in my amateur’s 2 cents:

Having lived in the Midwest most of my life (though not the Great Plains) I’ve paid a good bit of attention to tornadoes and storms over the years. I’ve seen many a weather map with the colliding cold air masses and the warm mist air coming up from the Gulf of Mexico. They collide often on that front from around central Texas on a line more or less NNE up through OK and KS. Sometimes that line is east a bit, sometimes west. When it is east, the collision of air masses puts the twisters into MO, IL, KY, IN and OH.

In my mind, that last key ingredient – storm-scale lift – is the trigger for tornadoes. The other three are the underlying conditions that, by themselves cannot create a tornado, only storms. Actually, the instability and wind shear are to a large degree, themselves IMHO part of the storm-scale lift. Thus the four ingredients are not, in themselves, the fundamental ingredients. The TWO fundamental ingredients are the warm, moist air mass and the cold, dense air mass. Those two are more basic than the four ingredients listed and what provide the four, more specific, ingredients.

We all know that the tornadoes are birthed at the southern end of what we call “the comma” – at its tip. I argue that there is a reason for this, and one that has not been addressed in storm science yet:

A cold air mass is a bubble that pushes under a warm air mass. In the center of that bubble the lift is more or less straight upward. However, on the edges of the bubble it is sloped, and there is a sloped component/vector where the bubble reaches down to the ground: The lift is not totally UP, but also at an angle. In the center of the air mass the lift makes for a rolling of the air into a horizontal tube and it never reaches the ground (but it may in fact be the reason for wind shear). But at the edge of the bubble the rolling tube starts out angled (visible in almost every photo and video of tornadoes), thus giving it the chance to reach down to the ground. The rolling tube starts out farther up, where the lift magnitude is greatest, but if there is enough rotational force being generated, it can entrain the air farther down and reach the ground. Many a tornado has begun higher up and then petered out before reaching the ground. The main point here is that the rolling tube that becomes a tornado forms ONLY at the sloping edge of the air mass. Its axis of rotation MUST have a tilt to it in order to reach downward into becoming a tornado. (The rolling tube in the center of the air mass cannot reach downward.)

Consistent with all that, what could be happening when warmer climate produces LESS tornadoes? My thinking is that the cold air mass is the necessary trigger, so if the cold air masses are less cold (less dense), they cannot provide enough storm-scale lift.

It is sad when the President of the AMS cannot see the difference between one side making wild statements with no basis in fact, and the other side, which uses facts to put the record straight.

Yes, but it is not just tornadoes. The ENTIRE skeptical effort is to “set the record straight” that has been skewed out of all proportions by the claims of CAGW activists (which includes the IPCC). Had the alarmists not made such bogus claims – including tornadoes – and created the entire global warming scare, the skeptics would have no reason to even exist.

Skepticism, pretty much by definition, is a reaction to weak or unfounded claims. Duh.